Abstract A cluster of computing systems is provided with guaranteed real-time access to data storage in a (SAN) Storage Area Network . Processes issue requests for bandwidth reservation which are initially handled by a daemon on the same node as the requesting processes. The local daemon determines whether bandwidth is available and, if so, reserves the bandwidth in common hardware on the local node; then forwards requests for shared resources to a master daemon for the cluster. The master daemon makes similar determinations and reservations for resources shared by the cluster, including data storage elements in the storage area network and grants admission to the requests that don't exceed total available bandwidth. Images: Description CROSS-REFERENCE TO RELATED APPLICATION(S) This application is related to and claims priority to U.S. provisional application entitled REAL-TIME STORAGE AREA NETWORK having serial No. 60/378,941, by Michael A. Raymond, ...